Aerobic digestion system for use in sewage treatment



April 3, 1962 R. F. MoGlvl-:RN 3,028,011

AEROBIC DIGESTTON SYSTEM FOR USE TN sEwAGE TREATMENT Filed Sept. 14,1960 5 Sheets-Sheet 1 www 4.

. "u 'I 23T INVENTOR. 2 ROBERT E MCGIVERN MAHONEY MILLEREL RAMBO ATTYS.

April 3, 1962 R. F. MGGIVERN AEROBIC DIGESTION SYSTEM FOR USE IN SEWAGETREATMENT Filed Sept. 14, 1960 3 Sheets-Sheet 2 ROBERT JF. MCGIVERNMAHONEY MILLER g. RAMBO ATTYS April 3, 1962 R. F. MoGlvl-:RN

AEROBIC DIGESTION SYSTEM F'OR USE IN SEWAGE TREATMENT Filed Sept. 14,1960 `5 sheets-sheet s INVENTOR. ROBERT F". M CGIVE-'N BY MAHONEY MILLER& RAMBO ATT 3,028,011 AEROBIC DIGESTION SYSTEM FOR USE IN SEWAGETREATMENT Robert F. MeGivem, R0. Box 3503, Beechwold Station, Columbus,Ohio Filed Sept. 14, 1960, Ser. No. 55,908 2 Claims. (Cl. 2111-220) Myinvention relates to an aerobic digestion system for use in sewagetreatment. It has to do, more specifically, with an aerobic digestionsystem for use in connection with the activated sludge process of sewagetreatment.

At the present time in the activated sludge process of sewage treatment,in order to obtain aerobic digestion, it has been customary to providetwo tanks, namely, a large aeration tank and a relatively small finaltank. The raw sewage enters the large tank and is subjected to a violentrolling or tumbling action by means of air under pressure dischargedinto the mixed liquor through suitably located submerged air diffusers.This resulting feeding of oxygen into the liquor brings about theaerobic digesting action and, after a suitable period, producing atreated liquid which is discharged into the final smaller tank. In thefinal smaller tank, the treated liquid is held for a suitable period, toallow settling of sludge, and is then discharged, usually into a stream,as treated sewage. It is necessary to return the sludge from the finaltank back to the aeration tank for further treatment by aeration and toreseed the mixed liquor but it will be understood that this is difficultto do because the nature of the sludge makes it difficult to provide areturn flow by gravity or even to force it back under pressure by meansof pumps. With this prior art process, there is difficulty in returningthe sludge from the final tank to the aeration tank.

It is the main object of my invention to provide an aerobic digestionsystem for use in the activated sludge process of sewage treatment whichuses a main aeration treating compartment for receiving the raw sewageand an associated final compartment into which the treated sewage isdischarged and which provides for the continuous and automatic return ofthe sludge from the final compartment back to the aeration compartmentfor further treatment.

Another object of my invention is to provide a system of the typeindicated which can be controlled readily to determine the rate at whichthe sludge from the final compartment is returned to the aerationcompartment.

A further object of my invention is to provide a system in which aviolent tumbling or rolling action is created in the aerationcompartment and the degree of this tumbling or rolling action can becontrolled.

A further object of this invention is to provide a system of the typeindicated in which the aeration action in the large compartment and thereturn of the sludge from the final compartment are related and arecontrolled simultaneously.

Another object of my invention is to provide a system of the typeindicated which employs a more simple tank arrangement and more simpleassociated apparatus than is employed with the prior art aerobicdigestion system of the activated sludge type sewage treatment process.

Various other objects will be apparent.

According to my invention, I provide a tank which is divided into alarge aeration treating compartment for receiving the raw sewage and asmaller connected final compartment for receiving the mixed liquor fromthe large compartment. The tank is divided by a bai-lle arrangementwhich will permit the continuous return of sludge from the finalcompartment to the aeration cornpartment. Associated with this baillearrangement are 3,028,011 Patented Apr. 3, 1962 ice air diiusers whichare so located that they not only provide means for causing the returnof the sludge from the final compartment to the aeration compartment butthey also serve to create the violent rolling or tumbling action in theaeration compartment. These air diflusers and the associated bailles areeither or both adjustable to vary the rate of return of the sludge fromthe final compartment and to vary the violence of the tumbling orrolling action in the aeration compartment.

In the accompanying drawings, I have illustrated the sewage treatingsystem of my invention and in these drawings:

FIGURE l is a transverse vertical sectional view taken along line 1--1of FIGURE 3 through a treatment tank in which my invention is embodied.

FIGURE 2 is a view similar to FIGURE 1 but showing the air dillusersadjusted to a different position.

FIGURE 3 is a longitudinal vertical sectional view taken through thetank substantially along line 3--3 of FIGURE l.

FIGURE 4 is an enlarged schematic detail of the baille arrangement andassociated air diffuser and illustrating the action of these units.

With reference to the drawings, I have illustrated apparatus in which myinvention is embodied and which consists of a large elongated tank 10preferably of rectangular form. This tank has an inlet 11 at one cornerthereof and adjacent its upper edge through which raw sewage isintroduced into the tank. The elongated tank is divided into twocompartments 12 and 13 by a baille unit 14 extending the full lengththereof. A passage or opening 15 is provided in the upper end of thebaille unit 14 at one corner thereof and leads from the compartment 12to the compartment 13, this passage being at a lower level than theinlet 11 and being adapted to conduct the treated or aerated liquid fromthe compartment 12 into the final compartment 13. From the compartment13 the final treated sewage liquid is discharged through an outlet 16.The inlet 11 for raw sewage and the outlet 16 for the final treatedsewage may be controlled by suitable valves. However, the circulationbetween the compartments 12 and 13 is continuous, as will later appear.

The baille unit 14 extends the full length of the tank 10 and,consequently, the compartments 12 and 13 will extend the full lengththereof. The baille unit comprises an upper baille or wall 21 whichextends throughout the greater portion of the depth of the tank and alower baille 22 which contacts or is set into the bottom 23 of the tank.The baffles 21 and 22 are in laterally inclined but parallelrelationship, the inclination being such that the final compartment 13is of substantially V-cross section transversely of the tank whereas thetreating compartment 12 has its side walls converging toward their upperends.

As indicated above, the baille 22 contacts the tank bottom 23 andextends upwardly and inwardly toward the longitudinal axis of the tank.Itoverlaps the lower portion of the baille 21 but is spaced inwardlythereof to provide a narrow chamber 25 between the overlapping portionsof the bafiles 21 and 22. This chamber is elongated and narrow,extending the full length of the tank, and has an upper outlet 26extending the entire length which opens upwardly into the treatingcompartment 12. The lower edge of the baille 21 is spaced from the tankbottom and provides an inlet 27 leading inwardly and upwardly into thechamber from the compartment 13.

For producing the swirling or tumbling action of the mixed liquor in thecompartment 12 and for returning sludge continuously from the narrowlower end of the compartment 13, I provide the air diffuser units 30.Each unit is of inverted T-form and comprises a `supply pipe 31 whichextends downwardly parallel to the baille 21 and which has a diiluserbranch 32 on its lower end. The branch 32 is provided with a pluralityof longitudinally spaced air outlet openings 33 which are directedupwardly. Any suitable number of units 30 may be provided but it will beunderstood that the branches 32 will extend substantially throughout thefull length of the tank (FIG- URE 3). The air diffusing branches 32 willbe located in the chamber 25 intermediate the height thereof (FIG- URESl and 2) or intermediate the lower edge 34 of the baille 21 and theupper edge 35 of the baille 22. The supply pipes 31 are connected bymeans of ilexible connections 37 to a manifold 36 which is connected tosuitable sources 39 of air under pressure. Each pipe 31 is carried by asupport 38 which extends the full length of the tank at the top sidethereof. Each pipe 31 is removably clamped by a supporting clamp 40 sothat each pipe 31 can be adjusted vertically to vary the level of itsassociated air diffuser branch 32 in the chamber 25. Thus, the space orchamber 25 provides a coniined passageway which establishescommunication between the lower ends of the compartments 12 and 13, andwhich is directed upwardly and inwardly from the narrow lower portion ofthe compartment 13 and into the compartment 12.

The baille 21 is preferably carried by screws 41 supported from thesupport 38 so that it can be adjusted vertically to vary the position ofits lower edge 34 relative to the tank bottom 23. The size of the inlet27 can be varied without varying the vertical position of the edge 34 byinserting baille blocks 42 (FlGURE 3) at spaced intervals along theinlet 27.

In the uses of this system, the baille 21 is adjusted so that its edge34 is spaced a suitable distance above the tank bottom 23 to provide aninlet 27 of suitable height. lf desired, the blocks 42 may be insertedin suitable number to vary the size and capacity of the inlet 27 butstill keep the edge 34 at a desired level. The pipes 31 will be adjustedvertically to adjust the diilusers 30 to proper levels in the chamber orrestricted passage 25. The tank compartment 12 is filled with mixedliquor and the treatment is started by introducing the air through thediffusers 30.

The air being forced from the diffuser branches 32 will be directedupwardly from the air outlets 33 through the chambers 25 and out theoutlet 26 into the compartment 12. It will be directed inwardly by theinclined baille 21 toward the opposite outer wall 44 of the compartment12. The specific gravity of the liquid in the compartment 12 above theoutlet 26 will be reduced and this will cause the entire body of mixedliquor in the tank 1li to roll counter-clockwise about its axis so as toaerate the liquid.

The aerated liquid will pass through the outlet into the upper wider endof the compartment 13, and some of the sludge will deposit therefrominto the narrow bottom portion of the iinal compartment 13. Due to theairlift action of the diifusers 30, this will draw sludge particlesupwardly from the bottom of the compartment 13 through the inlet 27 intothe chamber 25 and force it on upwardly into the compartment 12 where itwill join the swirling and tumbling mixed liquor therein and will beretreated, as indicated in FIGURE 4.

The extent of the rolling action in the aeration treating compartmentmay be controlled by the vertical position of the diffuser branches 32and the position of these branches in the chamber also controls thespeed of removal of the sludge deposit from the bottom of thecompartment 13. Also, the speed of removal of this sludge may becontrolled by the area of the inlet 27. Either or both of these controlarrangements may be employed in controlling the rate of removal ofsludge from t-he final compartment 13.

It will be apparent that I have provided an aerobic digestion system foruse in treating sewage which is much more eilective than prior artsystems. The system is continuous and the sludge is returned from thefinal compartment to the treating compartment more eiliciently. Also,simple, inexpensive apparatus can be used for the system.

Having thus described my invention, what I claim is:

l. A sewage treating system comprising a tank of substantiallyrectangular horizontal cross-section and being of suitable depth, avertically positioned baille unit in said tank spaced from opposed sideWalls thereof and extending the full length thereof to divide the tankinto a treating compartment for raw sewage and a final compartment, aninlet for raw sewage leading into the upper portion ot said treatingcompartment and an outlet for treated sew- `age leading from the upperportion of said ilnal compartment, said baille unit comprising a iirstbaille extending throughout the greater portion of the depth of the tankbut having its lower edge spaced from the bottom of the tank to providea space therebetween and having an opening in its upper portion forpermitting treated sewage to ilow from the treating compartment into thenal compartment, a second baille which is disposed inwardly of the firstbaille toward the treating compartment in spaced relationship therewith,said second baille extending from the bottom of the tank upwardly andoverlapping the ilrst baille to provide a narrow restricted passagehaving an outlet into the treating compartment at the upper edge of thesecond baille with the space at the lower edge of the first bailleserving as an inlet thereinto, and air diifusers in said passageintermediate the height of said second baille for aerating the sewage inthe treating compartment through said passage outlet and withdrawingsludge from the lower end of the iinal compartment through said passageinlet.

2. A sewage treating system comprising a tank of substantiallyrectangular horizontal cross-section and being of substantial depth, avertically positioned baille unit in said tank spaced from opposed sidewalls thereof and extending the full length thereof to divide the tankinto a treating compartment for raw sewage and a final compartment, aninlet for raw sewage leading into the upper portion of said treatingcompartment and an outlet for treated sewage leading from the upperportion of said final compartment, said baille unit comprising `a iirstbaille extending throughout the greater portion of the depth of the tankbut having its lower edge spaced from the bottom of the tank to providea space therebetween and having an opening in its upper portion forpermitting treated sewage to ilow from the treating compartment into thefinal compartment, `a second baille which is disposed inwardly of thefirst baille toward the treating compartment in spaced relationshiptherewith, said second baille extending from the bottom of the tankupwardly and overlapping the first bame to provide a narrow restrictedpas- 'sage having an outlet into the treating compartment at the upperedge of the second baille with the space at the lower edge of the iirstbaille serving as an inlet thereinto, and air diilusers in said passageintermediate the height of said second baille for aerating the sewage inthe treating compartment through said passage outlet and withdrawingsludge from the lower end of the final compartment through said passageinlet, said first baille extending at an angle outwardly toward theassociated side Wall so that the said iinal compartment is V-shape intransverse vertical cross-section with the inlet into said restrictedpassage being lat the converging lower portion of said iinalcompartment, `said second baille being in parallel relationship to theilrst baille, said `air diffusers being vertically adjustable in saidrestricted passage.

References Cited in the iile of this patent UNITED STATES PATENTS1,139,024 Frank May ll, 1915 2,473,323 Zack June 14, 1949 FOREIGNPATENTS 465,209 Germany Aug. 30, 1928

1. A SEWAGE TREATING SYSTEM COMPRISING A TANK OF SUBSTANTIALLYRECTANGULAR HORIZONTAL CROSS-SECTION AND BEING OF SUITABLE DEPTH, AVERTICALLY POSITIONED BAFFLE UNIT IN SAID TANK SPACED FROM OPPOSED SIDEWALLS THEREOF AND EXTENDING THE FULL LENGTH THEREOF TO DIVIDE THE TANKINTO A TREATING COMPARTMENT FOR RAW SEWAGE AND A FINAL COMPARTMENT, ANINLET FOR RAW SEWAGE LEADING INTO THE UPPER PORTION OF SAID TREATINGCOMPARTMENT AND AN OUTLET FOR TREATED SEWAGE LEADING FROM THE UPPERPORTION OF SAID FINAL COMPARTMENT, SAID BAFFLE UNIT COMPRISING A FIRSTBAFFLE EXTENDING THROUGHOUT THE GREATER PORTION OF THE DEPTH OF THE TANKBUT HAVING ITS LOWER EDGE SPACED FROM THE BOTTOM OF THE TANK TO PROVIDEA SPACE THEREBETWEEN AND HAVING AN OPENING IN ITS UPPER PORTION FORPERMITTING TREATED SEWAGE TO FLOW FROM THE TREATING COMPARTMENT INTO THEFINAL COMPARTMENT, A SECOND BAFFLE WHICH IS DISPOSED INWARDLY OF THEFIRST BAFFLE TOWARD THE TREATING COMPARTMENT IN SPACED RELATIONSHIPTHEREWITH, SAID SECOND BAFFLE EXTENDING FROM THE BOTTOM OF THE TANKUPWARDLY AND OVERLAPPING THE FIRST BAFFLE TO PROVIDE A NARROW RESTRICTEDPASSAGE HAVING AN OUTLET INTO THE TREATING COMPARTMENT AT THE UPPER EDGEOF THE SECOND BAFFLE WITH THE SPACE AT THE LOWER EDGE OF THE FIRSTBAFFLE SERVING AS AN INLET THEREINTO, AND AIR DIFFUSERS IN SAID PASSAGEINTERMEDIATE THE HEIGHT OF SAID SECOND BAFFLE FOR AERATING THE SEWAGE INTHE TREATING COMPARTMENT THROUGH SAID PASSAGE OUTLET AND WITHDRAWIGNSLUDGE FROM THE LOWER END OF THE FINAL COMPARTMENT THROUGH SAID PASSAGEINLET.